An intercalation-type catalyst such as lean NOx trap (LNT) and NOx storage catalyst (NSC) for abating NOx intercalates NOx as a nitrate salt into a basic intercalation material such as Ba, Ce, and the like on a support. Accordingly, emission of the NOx in a lean operating area in all diesel vehicles where the NOx may not be easily suppressed by a reaction on a noble metal due to a high oxygen concentration in exhaust gas relative to a theoretical air-fuel ratio may be suppressed by the intercalation-type catalyst. When the NOx is intercalated for a predetermined time, for example, several minutes to tens of minutes, the catalyst reaches a limit of NOx intercalation capability, and thus, when the oxygen concentration in exhaust gas is decreased through post injection, while a reduction component such as CO/HC and the like is increased, the intercalated nitrate is deintercalated and substantially reduced into N2 by a reducing agent such as HC, CO, H2, and the like.
The LNT catalyst may have NOx intercalation performance at a temperature ranging from about 100 to about 400° C. based on a catalyst temperature, and also NOx reduction performance at a temperature of greater than or equal to about 250° C. In particular, an LNT catalyst for a diesel engine may also have NOx intercalation performance at a low catalyst temperature due to its low exhaust temperature by additionally including Ce other than a conventional NOx intercalation material of Ba. The NOx is mainly reduced on Pt and Rh in a rich condition, but since the LNT catalyst for a diesel engine is maintained at a catalyst temperature of less than or equal to about 250° C., the NOx reduction may not be activated. For example, in a city-drive mode at a speed less than about 60 km/h, a substantial amount of the NOx may be released.